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| Author | Topic: Screw play |
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bobfoam Member Posts: 3 |
posted August 25, 2006 10:14 AM
   
Hello, Recently we have been checking the condition of our single screw extuder and have noticed some up and down movement of the screw while still within the barrel. When checking the tolerences between the barrel and screw, we found a gap of .052" to .053" at the top portion and 0" at the bottom. After observing this, we applied some up and down pressure and saw more play than expected. Is this normal, is there suppose to be more clearence at the top than the bottom? IP: Logged |
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Tom C Moderator Posts: 760 |
posted August 25, 2006 10:29 AM
2 issues; Your screw and barrel combination is worn out, that 0.50" gap should be 0.015" or less depending on your screw size. Large amounts of wear can cause low rates, poor melting, overheated melt, surging and other issues. The up and down movement is usually a result of a bent screw, or a bent barrel. This condition can cause a lot of wear. Please email me for inspection services, screw rebuilding, barrel alignment, or new screws and barrles. ------------------ Tom Cunningham www.ExtrusionTechnicalServices.com IP: Logged |
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bobfoam Member Posts: 3 |
posted August 25, 2006 02:06 PM
So for a 10inch diameter screw the tolerance shouldn't be greater than .015"? IP: Logged |
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Tom C Moderator Posts: 760 |
posted August 25, 2006 04:04 PM
Well since you did not mention size, I figured 4 1/2 or about. For a 10" barrel , and typical polymer processing, I would use this as a guidline for the screw diameter; New : 9.982 These numbers are subject to a lot of error based on barrel wear and the material being processed. Computer simulation can help to predict the effects of screw to barrel clearance while processing specific materials. ------------------ Tom Cunningham www.ExtrusionTechnicalServices.com IP: Logged |
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bobfoam Member Posts: 3 |
posted August 25, 2006 05:09 PM
Thanks Tom, If we can not get the problem paned out soon, we may give you a call. IP: Logged |
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